Stable phosphate esters

ABSTRACT

Esters of an acid of phosphorus such as tricresyl phosphate containing a stabilizing amount of a 2,5-bis-(4-pyridyl)-1,3,4thiadiazole are useful as lubricants or functional fluids at elevated temperatures in contact with metal surfaces.

United States Patent [191 Malec 1451 June 11, 1974 [5 STABLE PHOSPHATE ESTERS 3,228,888 l/l966 Spivack et al. .L 252/47 [75] Inventor: Robert E. Malec, Birmingham,

Mich. Primary ExaminerDaniel E. Wyman Assistant Examiner-Y. H. Smith [73] Asslgnee' Ethyl Corporation Rlchmond Attorney, Agent, or Firm-Donald L. Johnson; Robert [22] Filed: Feb. 19, 1971 A. Linn; Joseph D. Odenweller [21] Appl. No.: 117,094

7 [57] ABSTRACT (5 IIIIIIIIIIIIIII u g Esters of an acid of phosphorus such as tricresyl phosphate containing a stabilizing amount of a 2,5-bis-(4- [58] Field of Search 252/47, 49.8, 78, 46.7 pyridyn l3,4 thiadiazole are useful as lubricants or [56] References Cited functional fluids at elevated temperatures in contact 'th 1 UNITED STATES PATENTS meta Surfaces 3,1 15,465 12/1963 Orloff et al. 252/498 8 Claims, N0 Drawings BACKGROUND SUMMARY The objects of this invention are accomplished by providing an ester of an acid of phosphorus containing a stabilizing amount of a 2,5-bis(4-pyridyl)-l,3,4-

thiadiazole.

DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the present invention is a normally liquid ester of an acid of phosphorus suitable for use at high temperature in contact with metal surfaces containing a 2,5-bis(4-pyridyl)-1,3,4- thiadiazole. The ester can be any liquid ester of an acid of phosphorus including such acids as phosphoric, phosphonic, phosphinic, phosphorous, phosphonous,

phosphinous, phosphenic and phosphenous acid. The ester group can be alkyl, cycloalkyl, aryl, alkaryl or aralkyl, including halogenated alkyl, cycloalkyl, aryl, alkaryl, aralkyl, and the like. The preferred alkyl groups are those containing from I to about 50 carbon atoms, and the more preferred alkyls are those containing from about 3 to 30 carbon atoms, including their halogenated analogs. These include such alkyl groups as methyl, ethyl, 2-chloroethyl, 2-bromoethyl, propyl, isopropyl, 2-chloropropyl, 3-bromopropyl, butyl, isobutyl, 2-chlorobutyl, 2-bromobutyl, 2-chloroisobutyl, dodecyl, 2-chlorododecyl, tetradecyl, octadecyl, eicosyl, docosyl, 2-bromodocosyl, triacontyl, 2- chlorotriacontyl, tetracontyl, pentacontyl, 2- bromopentacontyl, 2-fluoropentacontyl, 2-

chloropentacontyl, and the like.

Some examples of esters resulting from the above alkyl groups are trimethyl phosphate, triethyl phosphate, tributyl phosphate, tridodecyl phosphate, trieicosyl phosphate, tri-triacontyl phosphate, dimethyleicosyl phosphate, methyl-dieicosyl phosphate, tripentacontyl phosphate, and the like, including their halogenated derivatives such as tri(2-chloropropyl)phosphate, tri(2-bromoeicosyl)phosphate, and the like. Further examples of alkyl esters include dimethyl hydrogen phosphonate, dimethyl methyl phosphonate, dibutyl methyl phosphonate, di(2- chloropropyl) hydrogen phosphonate, di(2- bromobutyl) bromobutyl phosphonate, and the like. Also included are methyl phosphinate, 2-chloropropyl phosphinate, isobutyl diisobutyl phosphinate, trimethyl phosphite, tributyl phosphite, methyl didodecyl phosphite, trieicosyl phosphite, methyl ditriacontyl phosphite, tri-tetracontyl phosphite, dimethyl pentacontyl phosphite, dimethyl phosphonite, didodecy] phosphonite, dipentacontyl phosphonite, dodecyl phosphinite,

2 eicosyl phosphinite, triacontyl phosphinite, butyl phosphenate, 2-chloroamyl phosphenate, 2- bromooctadecyl phosphenate, 2-chloropropyl phosphenite, 2-bromotriacontyl phosphenite, and the like.

The cycloalkyl esters include those in which the cycloalkyl group contains from about 6 to 8 carbon atoms, such as cyclohexyl, 3-chlorocyclohexyl, cycloheptyl, 4-bromocycloheptyl, cyclooctyl, 2- fluorocyclooctyl, 2-bromocyclooctyl, 2- chlorocyclooctyl, and the like. Exemplary esters are those listed above wherein the cycloalkyl groups are substituted for the alkyl radicals listed.

Preferred aryl and alkaryl groups include both the monoand di-nuclear radicals containing from 6 to about 30 carbon atoms. Mononuclear aryl and alkaryl groups containing from 6 to about 30 carbon atoms are preferred. These are termed phenyl groups which term includes alkyl-substituted phenyl and halosubstituted phenyl. Some examples are phenyl, 4- chlorophenyl, 2-bromophenyl, 2,4-dichlorophenyl, 2- methyl-phenyl, 3-methylphenyl, 4-methylphenyl, 3-methyl-4-chlorophenyl, 2-methyl-4v-bromophenyl,

2,4-dimethylphenyl, 2-ethylphenyl, 4-tert-butylphenyl,

3-octylphenyl, 2,4-didodecylphenyl, 2,4-dioctyl-3- bromophenyl, 4-eicosylphenyl, 4-triacontylphenyl, 3-tetracontylphenyl, 4-pentacontylphenyl, and the like. Typical resultant esters are triphenyl phosphate, tricresyl phosphate, tri(4-tert-butylphenyl)phosphate, phenyl dicresyl phosphate, cresyl diphenyl phosphate, tri( 4-chlorophenyl )phosphate, tri( 3methyl-4- bromophenyDphosphate, tri(4-hexylphenyl)- phosphate, 'diphenyl(4-dodecylpenyl)phosphate, 4 chlorophenyl di(4-eicosylphenyl)phosphate, diphenyl hydrogen phosphonate, diphenyl phenyl phosphonate, triphenyl phosphite, tricresyl phosphite, and the corresponding phosphenates, phosphonites, phosphenites, phosphinates and phosphinites.

Aralkyl esters of acids of phosphorus include those in which the aralkyl group contains from 7 to about 50 carbon atoms. Representative examples of such groups include benzyl, 2-phenylethyl, 4-bromobenzyl, 4- chlorobenzyl, 2,4-dichlorobenzyl, 4-dodecylbenzyl, 2- phenylbutyl, 2cresyldodecyl, 4-phenylbutyl, 2-(4- bromophenyl)ethyl, 2,2-diphenylhexyl, Z-phenyltetracontyl, 2-cresyltetracontyl, and the like.

The most preferred esters of a phosphorus acid are the esters of phosphoric acid. In particular, the aryl esters are preferred. Examples of these are diphenyl d0- decyl phosphate, cresyl dibutyl phosphate, diphenyl eicosyl phosphate, di(4-chlorophenyl)methyl phosphate, 4-bromophenyl ditriacontylphenyl phosphate, 4-chlorophenyl di( 2-chloropropyl )phosphate, di( 4- dodecylphenyl)dodecyl phosphate, 2-eicosylphenyl di- (4-bromo-2-methylphenyl)phosphate, and the like.

The most preferred stabilized esters are the triaryl phosphates, including the halogenated triaryl phosphates. Examples of these are tricresyl phosphate, phenyl dicresyl phosphate, cresyl diphenyl phosphate, tri(4-tert-butylphenyl)-phosphate, tri(2-tertbutylphenyl)phosphate, diphenyl 4-dodecylphenyl phosphate, phenyl di(4-eicosylphenyl)phosphate, 4- chlorophenyl di(4-triacontylphenyl)phosphate, di(4- bromophenyl) 4-pentacontylphenyl phosphate, tri(4-hexylphenyl)phosphate, tri(2- octylphenyl)phosphate, tri(2-secbutylphenyl)phosphate, de(4-hexylphenyl)2,4-

3 dihexylphenyl phosphate, phenyl(4-octylphenyl)(2,4- dioctylphenyl)phosphate, and the like.

The 2,5-bis(4-pyridyl)-l ,3,4-thiadiazole compounds are those having the formula:

in which n and p are integers from -2 and R, and R are lower alkyl groups containing 1-12 carbon atoms. Representative examples are 2,5-bis( 2-methyl-4- pyridyl l ,3 ,4-thiadiazole, 2,5 -bis( 2 ,6-dimethyl-4- pyridyl )-l ,3,4-thiadiazole, 2,5-bis-( 3-ethyl-4-pyridyl 1,3,4-thiadiazo1e, 2,5-bis( 2-n-butyl-4-pyridyl)- l ,3,4-

thiadiazole, 2,5-bis( 2-dodecyl-4-pyridyl )-1 ,3,4- thiadiazole, 2,5-bis( 2-hexyl-4-pyridyl)- l ,3,4- thiadiazole, 2,5-bis( 2,5-dioctyl-4-pyridyl 1 ,3,4- thiadiazole, 2,5 -bis( 2,5-dimethyl-4-pyridyl 1 ,3 ,4- thiadiazole, 2-( 2-methyl-4-pyridyl )-5-( 4-pyridyl l,3,4-thiadiazole, and 2-(2-octyl-4-pyridyl)-5-(4- pyridyl)-l,3,4-thiadiazole. The most preferred stabilizer is 2,5-bis(4-pyridyl)-l ,3,4-thiadiazole itself.

The thiadiazoles of the present invention are known compounds and are described by: Konig et al., Ber. 87, p. 825 (1954), McMillan et al., J. Am. Pharm. Assoc. 42, p. 457 (1953) and Van der Burg, Rec trav. chim, 74, p. 257 (1955).

The amount of stabilizer should be a stabilizing amount. This is a minor amount, sufficient to impart the required degree of stability under use conditions. Generally this is provided by adding from 0.005 to 5 weight per cent. A more preferred amount is from about 0.01 to 3 weight per cent.

The stabilizing compositions are readily made by merely adding the required amount of the 2,5-bis(4- pyridyl)-1,3,4-thiadiazole to the liquid ester and stirring until thoroughly blended. The following will serve to illustrate the preparation of some stabilized esters of this invention. All parts are by weight.

EXAMPLE 1 In a blending vessel place 10,000 parts of tricresyl phosphate and parts of 2,5-bis(4-pyridyl)-l,3,4- thiadiazole. Stir until throughly blended. The resultant ester is stable at high temperatures in contact with metal surfaces and is eminently useful as a turbine bearing lubricant at installations where a fire-resistant lubricant is required.

EXAMPLES 2 32 Repeat the procedure of Example 1 substituting in order the following esters:

dimethyl eicosyl phosphate tridodecyl phosphate tributyl phosphate dioctyl hydrogenphosphonate di( 2-chloropropyl) hydrogenphosphonate di( 2-bromobutyl)bromobutyl phosphonate butyl diisobutyl phosphinate trieicosyl phosphite didodecyl phosphonite triacontyl phosphinite dodecyl phosphenate 2-chlorooctyldecyl phosphenate 2-chloroeicosyl phosphonite tricyclohexyl phosphate tri( 3-chlorocyclohexyl )phosphate tri( 2-fluorocyclooctyl)phosphate tri( cyclohexyl)phosphite dicyclohexyl hydrogenphosphonate triphenyl phosphate tri(4-tert-butylphenyl)phosphate phenyldicresyl phosphate cresyldiphenyl phosphate tri(4-chlorophenyl)phosphate tri( 3-methyl-4-bromophenyl )phosphate tri(4-hexylphenyl)phosphate diphenyl(4-dodecylphenyl)phosphate 4-chlorophenyl di( 4-eicosylphenyl )phosphate diphenyl hydrogenphosphonate diphenyl phenyl phosphonate triphenyl phosphite tricresyl phosphite The resultant esters are more stable at elevated temperatures in contact with metal than the original unstabilized ester and are useful as lubricants and hydraulic fluids.

In a similar manner, each of the other alkylsubstituted 2,5-bis(4-pyridyl)-l,3,4-thiadiazoles disclosed can be substituted in Example 1 with good results.

The excellent stability provided by the present additives was shown using a Polyveriform Test carried out at 400 F. The test ester was placed in a cell together with magnesium, copper and steel coupons. The ester was heated to 400 F. and air bubbled through it for 72 hours. After this period, the acid number, percent viscosity increase and percent pentane insolubles were measured as criteria of degradation. The ester used in the test was a triaryl phosphate in which the aryl groups were mixtures of phenyl, hexylphenyl and octylphenyl radicals. The results obtained are shown in the following table.

As the results show, the addition of only a small amount of an additive of the present invention provided an ester of an acid of phosphorus having very high stability even at elevated temperatures in contact with metal surfaces. Such esters are useful as lubricants, especially for stationary turbine installations and as hydraulic fluids where a fire-resistant fluid of good viscosity properties is needed.

I claim:

1. A normally liquid ester of an acid of phosphorus suitable for use as a lubricant or hydraulic fluid at high temperatures in contact with metal surfaces selected from the group consisting of hydrocarbyl and halogenatecl hydrocarbyl esters of an acid of phosphorus containing a stabilizing amount of a compound selected from the group consisting of 2,5-bis(4-pyridyl)-l,3,4- thiadiazole and alkyl-substituted 2,5-bis(4-pyridyl)- 1 ,3,4-thiadiazoles.

2. A composition of claim 1 wherein said 2,5-bis-(4- pyridyl)- l ,3,4-thiadiazole is compound.

3. A composition of claim 2 wherein said acid is phosphoric acid.

4. A composition of claim 3 wherein said phosphate ester is an aryl phosphate aryl being selected from the phenyl.

5. A composition of claim 4 wherein said aryl is a triaryl phosphate.

group consisting of phenyl, alkylphenyl and halo- 5 *zg gg UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 5,816 Dated June 97 Inventoflfl Robert E. Male ppears in the above-identified patent It is certified that error a and that said Letters Patent are hereby corrected as shown below:

r- In column Claim 2 should read A composition of Claim 1 wherein said compound is 2,5-bis (H-pyridyD-lfifithiadiazole. In column 5, Claim L should read A composition of Claim 5' wherein said ester is an aryl phosphate, said aryl being selected from the group consisting of phenyl, alkylphenyl and halophenyl. Column 5, in

Claim 5, line 1, insert "phosphate" after "aryl" Signed and sealed this 1st day -of October 1974.

(SEAL) Attest:

McCOY Mo GIBSON JR. C. MARSHALL DANN Attesting Officer Commissioner of Patents 

2. A composition of claim 1 wherein said 2,5-bis-(4-pyridyl)-1, 3,4-thiadiazole is compound.
 3. A composition of claim 2 wherein said acid is phosphoric acid.
 4. A composition of claim 3 wherein said phosphate ester is an aryl phosphate aryl being selected from the group consisting of phenyl, alkylphenyl and halophenyl.
 5. A composition of claim 4 wherein said aryl is a triaryl phosphate.
 6. A composition of claim 5 wherein said triaryl phosphate is tricresyl phosphate.
 7. A composition of claim 5 wherein said triaryl phosphate is phenyl dicresyl phosphate.
 8. A composition of claim 5 wherein said triaryl phosphate is cresyl diphenyl phosphate. 